Fibrous tobacco smoke filter containing solid additive



G. P. TOUEY 2,917,054

FIBROUS TOBACCO SMOKE FILTER CONTAINING SOLID ADDITIVE Dec. 15, 1959Filed April 22, 1955 F/LAMENTS FIG.1.

FILTER WRAPPER R m H. F

' FIG. 2.

c/a/wsrrz WRAPPEK George R Touey INVENTOR. M 2 L 4 ATTORNEYS UnitedStates FIEROUS TUBACCD SMOKE FILTER CGNTAIN- ENG SOLE) ADDITIVEApplication April 22, 1955, Serial No. 503,183

4 "Claims. (Cl. 131-203) The present invention relates to tobacco smokefiltering material and elements thereof suitable for use in cigarettes,pipes, cigarette holders, and cigar holders. More particularly, theinvention is concerned with an improvement in filters of the generaltype disclosed in Crawford and Stevens U.S. Patents Nos. 2,794,239 and2,794,480 of June 4, 1957.

In the aforementioned patents, newly discovered advantages of a certaintype of fibrous tobacco smoke filter are discussed. The filter thereindescribed is prepared from a specially conditioned tow of syntheticallyspun continuous filaments and comprises a structurally unitary rod-likemass of fibers and a wrapper encircling the mass, each fiber of the massbeing substantially coextensive therewith, the fibers as a whole beingin substantial alignment longitudinally of the mass but substantiallyeach of the individual fibers having a plurality of short portionsthereof crimped into diverging and converging relationship to the mainfiber axis, a plurality of the fibers having surface solvation bonds tocontiguous fibers at random points of contact. Very good results havebeen obtained in the use of such filters for the removal of nicotine andtars from tobacco smoke, especially in view of the fact that the filterssupply other requirements, such as a unitary nature, rigidity, andresiliency, which are equally as necessary to the success of a tobaccosmoke filter.

These filters aiso have a marked processing advantage over other filtersknown in the art. However, since the fibers in such filters aregenerally parallel to each other, some channeling of the smoke throughthe filter may be possible.

In other words, while a desirable amount of interference with the smoothflow of combustion products through the channels is provided by therandom bonds between adjacent fibers, by the incompleteness of fiberorientation, and by the short fiber portions which are crimped intodiverging and converging relationship to the main fiber axis, yet alimited amount of the smoke passing through the filter apparentlytravels through channels in a smooth, non-turbulent and undisturbedmanner and thereby may be exposed to somewhat less than a theoreticallymaximum amount of impingement upon and contact with the solid surfacesof the filter. Experimental investigations have shown that any attemptto reduce the size or change the shape of the detrimentally smooth smokechannels through the filters by an increase in filter density eitherthrough greater compaction of the fiber mass or through the use of finerfibers generally also results in an intolerable increase in pressuredrop through the filter. It is also unsatisfactory to substantiallyincrease the amount of fiber crimp in order to obtain an increase in theamount of smoke 2,917,054 Patented Dec. 15, 1959" impingement byincreasing the number of divergent and convergent fiber portions.

In my copending U.S. patent application Ser. No. 413,950, filed March 3,1954, I have disclosed and claimed an improvement based on my discoverythat the efiiciency of filters of the type described above may besubstantially increased without the expected equivalent increase inpressure drop through the filters by preparing the filters with depositsof finely divided solid vegetable starch particles in the smoke channelsprovided by the spacing of adjacent fibers. The starch particles arecarried by and supported on the surfaces of the fibers. Among thepowdered, relatively pure starches specifically enumerated in the saidcopending application are those derived from wheat, potatoes, rice andtapioca.

I have now discovered that an impure, i.e., nonconcentrated starchymaterial (namely, ordinary wheat flour) provides a filtration efiiciencyequally as high as the relatively pure starches and exhibits anunexpected and advantageous distinction in that it adheres to the towfibers more firmly than most of the starch powders. Thus, during thefabrication, packaging, and use of the filters and cigarettes producedtherefrom, those filters containing wheat flour are completely resistantto being sifted out of the tow.

This invention, therefore, has as one object the production of anefiicient cigarette smoke filter consisting of a fibrous filteringmaterial, particularly a material comprising a bundle of substantiallylongitudinally oriented textile fibers infused with finely divided wheatflour particles. Another object is to provide means for increasing theefficiency of a cigarette filter prepared from a textile fiber. A stillfurther object is provision of a filter which is capable of removingnicotine, tars, and other deleterious components of cigarette smokewithout causing the smoke to be dry or distasteful. Another object is toincrease the efiiciency of tobacco smoke filters of the Crawford andStevens applications without creating a high pressure drop. Stillanother object is to provide a firmly adhering particulate additive forfibrous tobacco smoke filters, particularly those fibrous filtersprepared with fibers bonded through a coalescence obtained by means ofthe application of a spray of a liquid, solvent-type plasticizer. Otherobjects will be obvious from the present specification and claims.

Accordingly, the present invention consists, in general, in a fibroustobacco smoke filtering medium, for example, one comprising a mass ofsubstantially longitudinally aligned fibers, the spacing ofsubstantially all groups of adjacent fibers providing minute passagesfor smoke therethrough, said mass carrying therein finely divided wheatflour particles in an amount of 1 to by weight of the mass (theconcentration not being critical so long as there is sufficient wheatflour present to improve the filtration efiiciency of the filter withoutcreating excessive pressure drop), said particles being supported alongthe surfaces of and by the fibers and occupying positions along thewalls of and partially blocking said passages whereby a substantialportion of the smoke is impinged on the particles.

A more specific and very advantageous embodiment of the inventioncomprises a new tobacco smoke filtering material of synthetically spuncontinuous filaments and an element made therefrom, the elementcomprising a structurally unitary rod-like mass of fibers and a Wrapperencircling the mass, each fiber of the mass being substantiallycoextensive therewith, the fibers as a whole being in substantialalignment longitudinally of the mass but substantially each of theindividual fibers having a plurality of short portions thereof crimpedinto diverging and converging relationship to the main fiber axis, aplurality of the fibers having surface solvation bonds to contiguousfibers at random points of contact, the mass carrying substantiallyuniformly dispersed therein a solid finely divided wheat fiour in theamount of about 5 to 60% by weight of the mass.

Most advantageously, the invention comprises a filter of celluloseacetate fibers having surface solvation bonds achieved through theapplication of a plasticizer spray, the filter carrying un formlydispersed wheat flour partides in the amount of about 5 to 30% by weightof the filter.

Any suitable means known to the art for spreading a powder onto afibrous surface or through a fibrous mass may be employed in preparingfilters of the invention. Thus, for example, the wheat flour powder canbe blown onto the fibers or it can be ap lied as a slurry in cold wateror in a volatile organic vehicle or a plasticizer for the fiber. Anothermethod is to apply the fiour to the fibers electrostatically, i.e. toinduce a charge on the fibers by f iction or other suitable means andthen to run the fibers through a chamber containing a highlyconcentrated cloud of fiour dust. Preferably this is done with thefibers in the form of a tow and in a banded, i.e. spread-out condition.Still another method for applying the flour particles is to wet thesurface of the fibers with an adhesive or a plasticizer before exposingthem to a fiour spraying device. Preferably, the flour is continuouslyapplied to an opened and banded moving tow formed as described in theCrawford and Stevens patents. That is to say, tow from a supply roll isopened to debundlize the filaments and provide a larger and more uniformtow cross section. and the opened tow is spread uniformly to a muchlarger width of e.g.. times its original width, thereby exposingsubstantially all of the filaments to material, i.e. plasticizer,issuing from a dispenser adiacent which the tow passes. The flour may beadded before, simultaneously with, or after the plasticizer, preferablywith or after.

The invention is illustrated in the accompanying drawings in which Fig.1 represents a magnified view of the interior of a mass of filteringmaterial prepared in accordance with the invention, and

Fig. 2 is a view of cigarette having attached thereto a tip preparedfrom a filtering material of the invention.

The invention is further illustrated in the following examples:

EXAMPLE l.-FlLTRATION EFFICIENCY A partially opened tow of a crimped,regular crosssection cellulose acetate yarn (39.2% acetyl) having abouteight crimps per inch and containing approximately 12,- 000 filaments offive denier per filament was slowly pulled over a corresponding airbanding device as disclosed in the aforementioned Crawford and Stevenspatent applications and in Jackson US. patent application Serial No.356,983, filed May 25, 1953, now U.S. Patent No. 2,737,688 which spreadout the fibers to a width of about twelve inches. While the tow was inthis spread condition it was sprayed uniformly with finely divideddroplets of di-(methoxyethyl) phthalate plasticizer in order to makenumerous portions of the surfaces of the fibers adhesive. The spread towwas then passed through a dusting chamber which dusted the fibers with afinely divided (325 mesh) wheat flour of a type commercially availableand designated as bleached, enriched hard wheat fiour and said tocontain 14.0% protein, 67% starch and 13% moisture, the remainderconsisting of fats, sugars, and inert fibrous material. After thisspreading, spraying, and dusting, the tow was pulled back to itsoriginal shape of a cord and fed into a conventional cigarette make-upmachine which formed it cylindrically, wrapped it with paper, and cut itinto rods 78 mm. in length and 8 mm. in diameter. The rods had theapproximate composition of 25% flour, 14% plasticizer and 61% celluloseacetate by weight. The filter rods were then given a heat treatment forone hour at 80 C. to cause partial solvation of the acetate fibers bythe plasticizer and thereby bond the flour particles to the fibers andthe fibers to each other; imparting firmness to the rods. Thereupon therods were readily cut into 13 mm. filter tip lengths and attached toking-size cigarettes of a standard brand available on the retail marketin the US. The cigarettes were first shortened by 13 mm. and the rodsaflixed to the remainder by means of an adhesive tape. These filtercigarettes were smoked to a total butt length of 35 mm. on a smokingmachine similar in design and operation to the smoking machine describedby J. A. Bradford, W.R. Harlan and H. R. Hanmer in Industrial andEngineering Chemistry, vol. 28, pp. 836-9 (1936). The smoke which passedthrough the cigarettes was collected and analyzed for nicotine and tarcontent.

Control filters without a powdered additive were also prepared from thesame cellulose acetate yarn containing the same amount of plasticizer.These filters were attached to the same brand of standard king sizecigarettes shortened by 13 mm. These cigarettes were also smoked to atotal butt length of 35 mm. by means of the smoking machine. The smokewhich passed through the cigarettes was collected and analyzed fornicotine and tar content.

Ten unfiltered king size cigarettes which were not shortened by 13 mm.were smoked to a butt length of 35 mm. by means of the smoking machine.The smoke which passed through the cigarettes was collected and analyzedfor nicotine and tar content.

The results obtained from the three sets of cigarettes are listed inTable I.

1 Pressure drop in inches of water at an air flow rate of 17.5 cc.lsec.

From the results listed above it can be seen that the filter containingthe combination of acetate fibers and Wheat flour reduced the amount oftar collected by 38.5% and the amount of nicotine collected by 40%. Thecontrol filter reduced the amount of tars collected by 9.2% and theamount of nicotine collected by 8%. The increase in pressure drop of thefiltered cigarette due to the addition of the flour to the filter Wasonly about 5%.

EXAMPLE 2.LOSS OF ADDITIVE BY SIFTING OUT In order to determine howfirmly the wheat flour adheres to the fibers in the finished filterplug, a series of crimped cellulose acetate tow fibers containingvarious powders was prepared according to the procedure described in,Example 1. The cellulose acetate tow employed was identical to thatdescribed in Example 1 and contained the same kind and amount ofplasticizer sprayed on its surface. The types and amounts of powdersin-' corporated into the filter plugs are listed in the table below. Thedegree to which the powders adhered to the 78-min. filter plugs wasdetermined by dropping a plug in a vertical position a distance of 12inches onto a smooth glass surface. The plug was considered to resistsifting out of the powder if no visible amount of powder appeared on theglass surface after the plug was dropped six times in succession. Theresults of this drop test are also listed on the table below.

Type and Amount of Powdered Results of the 12" Drop Test Additive in thePlug Activated silica gel, 325 mesh, 22% Activated aluminum oxide, 325

mesh, 20%.

TracDe of powder after 1st drop.

Activated charcoal, 250 mesh, 18%. Do. Talc, 325 mesh, 20% Do. Calciumcarbonate, 325 mesh, 21% Do. Titanium oxide, 325 mesh, 15% D 0. Trace ofpowder after 2nd drop. Traclg of powder after 3rd drop.

Trace oipowder alter th drop.

In carrying out the operation of this invention, the type of Wheat flouremployed is not a critical factor. Rather, the form of the flour is moreimportant. The flour should be in a finely powdered form so that it canbe readily slurried in a liquid or passed through a spraying nozzle.While the exact size of the particles does not appear to be critical, itis indicated that the flour additive should be capable of passingthrough a 200 mesh screen and probably should be no finer than 500 mesh.Advantagcously, a flour is used which has at least 80% of its particlesof a diameter less than the diameter of the fibers of the filter. Nosubstantial number of particles should be as large as twice the filamentdiameter or as small as one-tenth the filament diameter. Any source offlour which passes this requirement can be employed. Such commercialtypes of wheat flour as bleached, unbleached, whole-wheat, whole bran,selfrising and the like may be employed.

While unusually good results have been obtained with filters preparedfrom a crimped continuous filament tow of cellulose acetate fiberssprayed with a plasticizer, e.g. di-(methoxyethyl)phthalate ormethylphthalylethylglycolate, it will be recognized by those skilled inthe art that the usefulness of the invention extends to other fibrousfilters, including those prepared from such fibers for example, ofviscose, cotton, nylon, polyamides, polyesters, particularly where thefibers are in substantial longitudinal alignment and are coextensivewith the body of the filter. It is preferred to use for filterpreparation in accordance with the present invention a continuousstrand, e.g. tow, of 4,000 to 35,060 filaments, the filaments being of16 to 3 denier and having about 4 to 10 crimps per inch.

By the expression surface solvation as used herein is meant thecreation, by the action of a solvent or plasticizer and/or heat, of anadhesive, tacky or readily bonding condition of the filaments bysolution or incipient solution of surface portions of the filamentmaterial whereby there is produced a welding and adhesion betweenadjacent filaments contacting at such portions, and by coalescence" ismeant the situation caused by partial or incipient solvation of surfaceportions of the filaments and resulting in a condition within thoseportions under which the portions will flow into or unite with similarportions of dissolved or plastic material in contiguous filaments.Surface solvation bonds between fibers are sometimes also referred to asfused or welded bonds.

It is to be noted that while the filters of the present invention seemto derive special benefits from the properties and behavior of wheatflour itself, yet the invention, in essence, appears to be dependentupon the structural character of the filter. In this regard, the moreimportant structural factors found in the most advantageous form of theinvention seem to be:

(1) That the aligned filaments be randomly bonded at 6 randomly spacedintervals. This may be achieved by spraying a solvent type ofplasticizer onto a spread tow of synthetic thermoplastic filaments asdescribed above. It also may be accomplished by use of a filament strandin which at least some of the filaments contain sufficient plasticizerto be softened at slightly elevated temperatures.

(2) That the filament bonds be formed by coalescence of the surfacesolvation type. In other words, no material should be employed foradhering the filaments which would coat, destroy or otherwisesubstantially interfere with the integrity of the wheat flour particles.Obviously no plasticizer should be employed which has a solvent orsoftening action on the flour particles. Bonds formed by coalescence ofthe surface solvation type also may be attained through the use offilaments spun with a suitable plasticizer content.

(3) That substantially all the flour particles be carried on thesurfaces of the filaments, supported by the filaments, and substantiallyimmobile with respect thereto. This structure is best accomplished bysoftening of portions of the filament surfaces whereby the particles maybe slightly embedded therein without being coated or covered. It is alsomost easily accomplished when the diameters of the particles are not toodifferent from the diameters of the filaments, the major portion of theparticles being, for instance, less than twice the filament diameter,but more than one-tenth of the filament diameter.

I claim:

1. A tobacco smoke filtering element made up of a bundle of co-extensivefilaments in which all of the filaments are generally longitudinallyoriented in said bundle, the filaments making up the bundle beingcharacterized in that said filaments:

a. Comprise approximately 12,000 filaments of cellulose acetate havingan acetyl content of 39.2% and a denier of 5 per filament;

I]. Are continuous filaments having about 8 crimps per inch;

c. Carry a content of plasticizer from the group consisting ofdi(methoxyethybphthalate or methylphthalylethylglycolate and also acontent of wheat flour of 325 mesh bound to said filaments by means ofsaid plasticizer so as to resist sitting out;

said bundle being characterized in that certain of the coextensivefilaments by means of the plasticizer are coalesced to otherco-extensive filaments within the bundle at randomly spaced intervals togive a filter element having the approximate composition by weight of61% cellulose acetate, 25% flour and 14% plasticizer, said filter beingpervious along its longitudinal axis.

2. A tobacco smoke filtering element made up of a bundle of co-extensivefilaments in which. all of the filaments are generally longitudinallyoriented in said bundle, the filaments making up the bundle beingcharacterized in that said filaments:

a. Are of cellulose acetate;

b. Arc of crimped continuous filaments;

c. Carry a content of plasticizer and finely-divided wheat flourparticles in which at least of the particles are of a diameter less thanthe diameter of the filaments, said fiour being bound to saidplasticizer so as to resist sifting out;

said bundie being characterized in that certain of the coextensivefilaments within the bundle are coalesced to other coextensive filamentsat randomly spaced intervals, said filter being pervious along itslongitudinal axis.

3. A tobacco smoke filtering element made up of a bundle of co-extensivefilaments in which all of the filaments are generally longitudinallyoriented in said bundle,

1 8 the filaments making up the bundle being characterized coextensivefilaments at randomly spaced intervals, said I in that said filaments:filter being pervious along its longitudinal axis.

Ar of ll l s et References Cited in the file of this patent b. Are ofcrimped continuous filaments; 5 c. Carry a plasticizer and 530% byWeight of line UNITED STATES PATENTS ly-divided Wheat flour of particlesize within the range 13091529 Pettlbo'ne June 9, '1931 f 200400 mesh;1,845,264 Grunauer Feb. .16, 19.32. 2,331,830 Garber Oct. 12, 1943 saidbundle being characterized in that certain of the 7 ath op et al- Mar.27, 1945 coextensive filaments by means of the plasticizer are co-2,664,374 Slayter et a1. Dec. 29, 1953 alescecl to other coextensivefilaments within the bundle 2,688,380 MacHenry Sept. 7, 1954 at randomlyspaced intervals, said filter being pervious 2,707,3 8 Taylor et a1. May3, 1955 along its longitudinal axis. 2,739,913 Lieser Mar. 27, 1956 4. Atobacco smoke filtering element made up of a 2,751,320 Jac bs et a1.June 19, 1956 bundle of co-extensive filaments in which all of the fila-2,763,267 Muller Sept. 18, 1956 ments are generally longitudinallyoriented in said bundle, 2,774,630 aC Y 1 19 6 the filaments making upthe bundle being characterized 2,780,228 Touey Feb. 5, 1957 in that saidfilaments: 2,789,563 Taylor et al. Apr. 23, 1957 a. Are of thermoplasticfilaments which are con- 20 FOREIGN PATENTS .tinuous and crimped;189,399 Switzerland May 1, 1937 b. Carrya content of plasticizer and offinely-divided 289,058 SWitZerlfind June 16, 1953 Wheat fiour attachedto said filaments in a manner 440,316 Great Brit in Dec. 24, 1935whereby the flour resists sifting out; 538,529 Gmat Bf 1ta 1n Aug 1941653,666 Great Britain May 23, 1951 said bundle being characterized inthat certain of the 665,278 Great Britain Jan. 23, 1952 coextensivefilaments Within the bundle coalesced to other 1,101,035 France Apr. 13,1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.2,917 ,054 December 15, 1959 George P0 Touey It is hereby certified thaterror appears in the printed specification of the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 3, line 59, for "corresponding" read compressedcolumn 7, line 27,for "bundle coalesced" read bundle are coalesced Signed and sealed this21st day of June 1960 (SEAL) Attest:

KARL H. AX ROBERT C. WATSON Attesting Officer Commissioner of Patents

1. A TOBACCO SMOKE FILTERING ELEMENT MADE UP OF A BUNDLE OF CO-EXTENSIVEFILAMENTS IN WHICH ALL OF THE FILAMENTS ARE GENERALLY LONGITUDINALLYORIENTED IN SAID BUNDLE, THE FILAMENTS MAKING UP THE BUNDLE BEINGCHARACTERIZED IN THAT SAID FILAMENTS: